Load-lifting and orienting devices have been known and used in the past. Generally, these devices are quite complex in construction and operation and are expensive to produce and maintain. Disclosures relating to this general subject matter are found in U.S. Pat. Nos. 2,020,306, 2,412,488 and 3,541,888.
U.S. Pat. No. 2,020,306 shows a load-lifting apparatus having a beam and a pair of sheaves mounted on a rotatable shaft for lifting a load from a vehicle. A pair of cables are connected to the lower of the load and the cables are wound around the sheaves. A motor which drives a worm rotates a worm gear coupled to the shaft. The patent states that when the motor is not operating, the worm will hold the sheaves stationary.
U.S. Pat. No. 2,412,488 shows a load-lifting apparatus including a frame having end blocks so that a screw can be rotated by a crank arm to shift a hoist cage along the length of the frame to equalize a load. Chains are secured to a load, such as a vehicle engine, and a screw is rotated so that the cage is approximately in the center of the frame. The hoist is lifted until the engine is raised a slight distance, and the cage is repositioned along the length of the frame so that the weight of the engine is equalized between the supporting chains.
U.S. Pat. No. 3,541,888 discloses a worm which can be used to prevent uncontrolled reverse rotation of a winch assembly comprised of a winch drum and a rope.
Because of the drawbacks and problems associated with prior load-lifting and orienting structures of conventional design, a need exists for improvements in this type of mechanical equipment and the present invention satisfies this need.